If you have a good relationship with your doctor, then you might try getting in touch with them directly. Either that or make sure that your doctor has instructions on your account that you can get squeezed in and to not brush you off like that. I know that when I need to see my doctor (I have 2 that I see, actually), but anytime that I have an important reason to go, I either get in the same day or the next, and both have rather difficult schedules. If I can't get in to see one (sort of my primary), then I always make a call to the other and can get squeezed in.